Presenter: Ondrej Masek, University of Edinburgh, Scotland
Abstract: Biomass consists of four main constituents, cellulose, hemicellulose, lignin and minerals. The first two, and to some extent also lignin are the key targets for various conversion processes producing biofuels and chemicals. Minerals on the other hand are a by-product whose potential is yet to be realized. As biomass production requires minerals, such as N, P, K and others, the natural way to use this bio-refinery side-stream is as a fertilizer, closing the nutrient cycle. However, depending on the form of mineral residues, direct application to land may not be an option. Even if the minerals are in a form acceptable for land application, it may not be the most effective way, as nutrients supplied in this way are prone to leaching, and a different form of fertilizer, one with controlled release rate is needed.
Such product can be obtained by combining extracted minerals with another bio-refinery by-product, lignin, and subsequent thermal treatment of this blended material. This could be a particularly advantageous way of utilizing and adding value to low-quality lignins that are difficult to use for other high value applications. This is true not only for biorefineries using terrestrial biomass, but also for those utilising marine biomass (with typically high mineral content). In addition, due to carbonization of lignin, the resulting product could be viewed as biochar, and therefore offer carbon sequestration potential, in form of storage of solid stable carbon in soils. Results of research in these areas will be presented.
In conclusion, recovery and re-cycling of nutrients is an important aspect of bio-refineries, to achieve environmental sustainability, and this process can be made more efficient by utilizing synergies with other bio-refinery co-products, especially lignin. Combined densified and thermally treated mineral-lignin composites have the potential to be a high quality fertilizer product, with added carbon sequestration benefit.